Quantitative marinating and dynamic air-drying method for instant marinated duck necks

Abstract

This invention discloses a quantitative braising and dynamic air-drying method for ready-to-eat braised duck necks, relating to the field of meat processing technology. The method includes: S1 microenzymatic hydrolysis, where the duck necks are placed in a permeation solution containing calcium chloride and flavor enzymes for segmented temperature-controlled enzymatic hydrolysis; S2 vacuum low-temperature wet braising, where a wet braising solution containing basic seasonings and a first portion of spice extract is added at a quantitative liquid-to-material ratio under vacuum conditions; S3 pulsating vacuum-assisted permeation, alternating between vacuum and normal pressure states; S4 edible composite coating, where the duck necks are immersed in a coating solution containing chitosan, sodium alginate, reducing sugars, and amino acids; S5 micro-fermentation coupled with dynamic air-drying, where the duck necks are inoculated with *Lactobacillus plantarum* and *Hansellechneria natans* followed by gradient temperature and humidity air-drying; S6 low-heat Maillard flavoring; S7 biological preservation treatment; and S8 rapid cooling with liquid nitrogen followed by vacuum packaging. This invention achieves the endogenous generation and effective preservation of flavor substances through the synergistic effects of microenzymatic hydrolysis, vacuum low-temperature wet braising, micro-fermentation coupled with air-drying, and segmented flavoring.

Description

Technical Field

[0001] This invention relates to the field of meat processing technology, and more specifically, to a quantitative braising and dynamic air-drying method for ready-to-eat braised duck necks. Background Technology

[0002] Braised duck necks are a popular ready-to-eat snack meat product. Their flavor and quality primarily depend on the penetration efficiency of spices during the braising process and the retention of flavor compounds during air-drying. Currently, industrial production of braised duck necks often employs the traditional excessive broth braising process, where the duck necks are submerged in a large amount of braising liquid for an extended period and then naturally air-dried or hot-air dried. This process has several shortcomings in practical application: First, the braising process mainly relies on the passive dissolution of spice flavor components in the braising liquid and the natural diffusion driven by the concentration gradient. The rate at which flavor substances penetrate into the duck neck is relatively slow, and the complex structure of the duck neck bone and meat leads to uneven flavor distribution. At the same time, some components in the spices are not fully utilized.

[0003] Secondly, the high-temperature and long-term braising process causes some heat-sensitive flavor components to volatilize and dissipate during processing, and the duck neck muscle protein undergoes excessive denaturation under continuous high temperature, which has an adverse effect on the final texture of the product.

[0004] Third, the braising and air-drying processes operate relatively independently. The air-drying process mainly involves physical dehydration, and flavor substances are lost during the evaporation of water. There is a lack of process design to actively regulate and fix flavor components during the dehydration stage.

[0005] Fourth, in traditional processes, spices are usually added to the brine all at once. Different boiling point flavor components have different degrees of dissipation during the subsequent long heating and drying process. The retention rate of low boiling point aroma components is relatively low, which affects the overall flavor profile and fullness of the product. Therefore, a quantitative braising and dynamic air-drying method for ready-to-eat braised duck necks is proposed to address the above problems. Summary of the Invention

[0006] In order to overcome the above-mentioned defects of the prior art, the present invention provides a quantitative braising and dynamic air-drying method for ready-to-eat braised duck necks, which aims to solve the problems of insufficient flavor penetration efficiency and distribution uniformity, easy loss of heat-sensitive flavor components during processing, loss of flavor substances during the air-drying stage, and incomplete preservation of spice flavor layers in the existing process.

[0007] To achieve the above objectives, the present invention provides a quantitative braising and dynamic air-drying method for ready-to-eat braised duck necks, comprising the following steps: S1 Microenzymatic Hydrolysis: The pretreated duck necks are placed in a permeate solution containing calcium chloride and flavor enzymes for segmented temperature-controlled enzymatic hydrolysis. In this step, calcium chloride activates the endogenous calpain in the duck necks, which works synergistically with exogenous flavor enzymes to hydrolyze muscle proteins into small peptides and free amino acids under segmented temperature conditions, providing a reserve of flavor precursors for subsequent thermal processing.

[0008] S2 Vacuum Low-Temperature Wet Braising: The duck necks treated in S1 are placed under vacuum conditions, and a wet braising liquid consisting of basic seasonings, the first part of the spice extract, and water is added at a quantitative liquid-to-material ratio for braising. The vacuum environment helps the braising liquid to fully contact the duck neck tissue, the low temperature reduces the volatilization and loss of heat-sensitive flavor components, and the quantitative liquid-to-material ratio reduces the amount of braising liquid used while ensuring the braising effect.

[0009] S3 Pulsating Vacuum-Assisted Infiltration: The duck necks braised in S2 are alternately circulated between vacuum and normal pressure in a sealed container. This step utilizes the alternating pressure changes to cause the duck neck tissue to repeatedly expand and contract, creating a pressure-driven mass transfer effect that promotes the migration of flavor substances in the brine to deeper tissues and improves the uniformity of flavor distribution.

[0010] S4 Edible Composite Coating: The duck necks treated in S3 are immersed in a coating solution composed of chitosan, sodium alginate, glycerol, reducing sugars, amino acids, and water. This step forms an edible film layer embedded with reducing sugars and amino acids on the surface of the duck necks. The combination of chitosan and sodium alginate provides good film-forming properties and mechanical strength, while glycerol acts as a plasticizer to improve the flexibility of the film layer. The reducing sugars and amino acids embedded in the film layer provide a reserve of reaction substrates for the subsequent Maillard reaction. At the same time, the film layer can reduce the loss of flavor components to a certain extent during the subsequent air-drying process.

[0011] S5 Micro-fermentation Coupled with Dynamic Air Drying: The surface of the duck neck coated in S4 is inoculated with a compound fermentation agent composed of *Lactobacillus plantarum* and *Hansenula d'Barry*. After inoculation, dynamic air drying is carried out under gradient temperature and humidity conditions. In this step, the first stage of medium temperature and high humidity conditions provides a suitable growth and metabolic environment for the inoculated strains, and *Lactobacillus plantarum* and *Hansenula d'Barry* produce flavor metabolites such as lactic acid and esters, respectively. As the temperature gradually increases and the humidity gradually decreases, the fermentation process naturally transitions to the air drying and dehydration stage, allowing the flavor substances to be concentrated during the dehydration process.

[0012] S6 Low-Heat Maillard Flavor Enhancement: The S5 air-dried duck necks are kept at a constant temperature below the braising temperature. This step allows the reducing sugars and amino acids embedded in the coating layer to undergo a Maillard reaction under mild heating conditions, generating soy sauce flavor substances that adhere to the product surface. The constant temperature is within the range where the Maillard reaction occurs mildly, which can obtain a suitable flavor intensity without excessive browning.

[0013] S7 Bio-preservation Treatment: The surface of the duck necks after S6 flavor enhancement is coated with a composite bio-preservative solution, which is composed of nisin, ε-polylysine, natamycin, chitosan, and water. This step utilizes the combination of nisin, ε-polylysine, and natamycin to achieve broad-spectrum antibacterial effects against Gram-positive bacteria, Gram-negative bacteria, and fungi. Chitosan acts as a film-forming carrier, enhancing the adhesion of the preservative solution to the surface of the duck necks and exhibiting a synergistic antibacterial effect, forming an antibacterial barrier on the surface of the duck necks.

[0014] S8 Rapid Cooling and Shaping: The duck necks treated in S7 are rapidly cooled with liquid nitrogen and then vacuum-packed. This step quickly lowers the core temperature of the duck necks to the refrigeration temperature, which helps to fix the distribution of flavor substances formed in the previous steps. At the same time, the rapid passage through the active temperature range of microorganisms helps to reduce the loss and oxidation of flavor substances during the cooling process.

[0015] Furthermore, in the S1 microenzymatic hydrolysis treatment, the mass fraction of calcium chloride in the permeate is 0.2%-0.6%, and the mass fraction of the flavor enzyme is 0.1%-0.3%. The segmented temperature-controlled enzymatic hydrolysis is maintained in three temperature ranges: 4℃-10℃, 25℃-30℃, and 40℃-45℃. These concentration ranges ensure effective activation of endogenous calpapsin by calcium chloride and appropriate hydrolysis of proteins by the flavor enzyme. The segmented temperature settings correspond to the activation of endogenous enzymes, the initiation of exogenous enzymes, and the main reaction stage of exogenous enzymes, respectively, allowing each enzyme system to exert its catalytic effect within a suitable temperature range.

[0016] Furthermore, in the S2 vacuum low-temperature wet braising process, the vacuum level is -0.06 MPa to -0.09 MPa, the quantitative liquid-to-material ratio is 0.8:1 to 1.2:1, and the braising temperature is 55℃-65℃. The above vacuum level range maintains a suitable negative pressure environment during the braising process. The quantitative liquid-to-material ratio reduces the amount of braising liquid used while ensuring sufficient contact between the braising liquid and the duck necks. The braising temperature, lower than conventional braising temperatures, helps reduce the volatilization loss of heat-sensitive flavor compounds.

[0017] Furthermore, in the S3 pulsed vacuum-assisted permeation, the alternating vacuum pressure ranges from -0.08 MPa to -0.09 MPa, with a single cycle lasting 5-8 minutes and 3-6 cycles. These parameter settings allow the duck neck tissue to undergo regular expansion and contraction during the alternation of vacuum and atmospheric pressure, resulting in an effective pressure-driven mass transfer effect.

[0018] Furthermore, in the S4 edible composite coating, the coating solution contains 1.0%-2.0% chitosan, 0.5%-1.0% sodium alginate, 1.0%-2.0% glycerol, 1.0%-2.0% reducing sugar, and 0.3%-0.8% amino acids. The combination of chitosan and sodium alginate forms a film with good film-forming properties and mechanical strength. Glycerol improves the flexibility of the film, and the reducing sugar and amino acids are embedded in the film in a suitable ratio to provide reaction substrates for the subsequent Maillard reaction.

[0019] Furthermore, in the S5 micro-fermentation coupled dynamic air drying, the gradient temperature and humidity conditions are as follows: the first stage temperature is 30℃-35℃ and the relative humidity is 70%-80%, the second stage temperature is 40℃-45℃ and the relative humidity is 60%-70%, and the third stage temperature is 50℃-55℃ and the relative humidity is 45%-55%. The inoculum size of *Lactobacillus plantarum* was 1 × 10⁻⁶. 7 CFU / g up to 5×10 7 The inoculum size of CFU / g duck neck raw material is 5×10⁻⁶ Hnsenula polymorpha. 6 CFU / g up to 2×10 7 CFU / g duck neck raw material. The first stage, with medium temperature and high humidity, provides a suitable growth and metabolic environment for the inoculated strains. Under their respective suitable conditions, Lactobacillus plantarum and Saccharomyces hansonii produce flavor metabolites such as lactic acid and esters. As the temperature and humidity conditions change gradually, the fermentation process gradually transitions to the air-drying and dehydration stage.

[0020] Furthermore, in the S6 low-heat Maillard flavoring process, the temperature below the brining temperature is 65℃-75℃, and the holding time is 15min-30min. This temperature range is within the range where the Maillard reaction occurs mildly, allowing the reducing sugars and amino acids in the coating layer to react and generate soy sauce flavor substances without excessive browning. Within the holding time range, the degree of reaction can be controlled to obtain a suitable flavor intensity.

[0021] Furthermore, in the S7 biological preservation treatment, the concentration of nisin in the composite biological preservation solution is 1.5 g / L-2.5 g / L, the concentration of ε-polylysine is 2.0 g / L-3.0 g / L, the concentration of natamycin is 0.8 g / L-1.5 g / L, the concentration of chitosan is 1.0 g / L-2.0 g / L, and the pH value of the composite biological preservation solution is 4.5-5.0.

[0022] The combination of nisin, ε-polylysine and natamycin can achieve broad-spectrum antibacterial effects against Gram-positive bacteria, Gram-negative bacteria and fungi. Chitosan, as a film-forming carrier, enhances the adhesion of the preservative solution to the surface of duck necks and has a synergistic antibacterial effect. The pH range helps the activity of each preservative component to be stable.

[0023] Furthermore, in the S8 rapid cooling and shaping process, the liquid nitrogen rapid cooling reduces the center temperature of the duck neck to below 4°C within 10 minutes. After rapid cooling, the duck neck is left to stand in a 4°C environment for 30-60 minutes before vacuum packaging. The rapid cooling within 10 minutes allows the duck neck to quickly pass through the temperature range where microorganisms are most active, which helps to reduce the loss and oxidation of flavor substances during the cooling process. The standing time allows the internal and external temperatures of the duck neck to become more uniform before vacuum packaging.

[0024] Furthermore, the first portion of spice extract is one or more of clove extract, cinnamon extract, and star anise extract; Before maintaining the constant temperature in S6, the second part of the spice extract is atomized and sprayed onto the surface of the duck neck. The second part of the spice extract is one or more of the following: Sichuan pepper extract, cardamom extract, and galangal extract. After the S6 constant temperature maintenance ends and before the S7 biological preservation treatment, the third part of the spice extract is atomized and sprayed onto the surface of the duck neck. The third part of the spice extract is fennel extract or Sichuan pepper low boiling point component extract. The mass ratio of the first, second, and third spice extracts is (4-6):(2-3):(1-2). By grouping the spice extracts according to different boiling point characteristics and adding them at different process stages, the first part is added during the braising stage to ensure full penetration of the basic flavor, the second part is added before aroma enhancement to supplement the medium-boiling-point aroma components, and the third part is added at the end of the process to retain the low-boiling-point aroma components to the greatest extent. The mass ratio of the three parts ensures that the high-boiling-point components are the main components, the medium-boiling-point components are the auxiliary components, and the low-boiling-point components are supplemented in an appropriate amount, which helps to improve the integrity and fullness of the spice flavor of the product.

[0025] Compared with the prior art, the beneficial effects of the method described in this invention are mainly reflected in the following aspects: First, addressing the issues of flavor penetration efficiency and distribution uniformity, this invention employs a S1 microenzymatic hydrolysis step, placing the duck necks in a permeation solution containing calcium chloride and flavor enzymes for segmented, temperature-controlled enzymatic hydrolysis. Calcium chloride activates the duck neck's endogenous calpain system, which synergistically works with exogenous flavor enzymes on muscle proteins to produce small peptides and free amino acids, providing flavor precursors for subsequent processing. Simultaneously, the S2 vacuum low-temperature wet braising process, combined with the S3 pulsed vacuum-assisted permeation step, ensures sufficient contact between the braising liquid and the duck neck tissue. The pulsed vacuum circulation causes the duck neck tissue to repeatedly expand and contract under alternating pressure, promoting the migration of flavor substances from the braising liquid to deeper tissues and improving the uniformity of flavor distribution.

[0026] Secondly, addressing the issue of heat-sensitive flavor components being easily lost during processing, this invention employs the S2 vacuum low-temperature wet braising method, braising at a lower temperature range of 55°C to 65°C. Compared to traditional high-temperature braising, this reduces the volatilization and loss of heat-sensitive flavor substances. Simultaneously, the low temperature helps control the degree of muscle protein denaturation, positively impacting the preservation of product texture. The coating of the compound biological preservation solution in the S7 biological preservation step allows for subsequent low-intensity sterilization treatments, further reducing the damage to flavor components caused by secondary heating.

[0027] Third, addressing the issue of flavor substance loss during the air-drying stage, this invention employs a synergistic control mechanism through a coupled dynamic air-drying step involving an edible composite coating (S4) and micro-fermentation (S5). The reducing sugars and amino acids embedded in the coating solution form an edible film on the surface of the duck neck. In the subsequent low-heat Maillard flavoring step (S6), a Maillard reaction occurs at 65°C to 75°C, generating a soy sauce-like flavor substance that adheres to the product surface. Simultaneously, the *Lactobacillus plantarum* and *Baryia henselae* inoculated in step S5 undergo metabolic activity under gradient temperature and humidity conditions, producing lactic acid, esters, and other flavor substances. The air-drying process simultaneously concentrates these flavor substances, partially compensating for the flavor loss during the dehydration stage.

[0028] Fourth, addressing the issue of incomplete preservation of spice flavor layers, this invention divides the spice extract into three parts based on different boiling point characteristics and adds them separately at different process stages. The first part is added during the S2 brining stage to ensure full penetration of the basic flavor; the second part is sprayed before the S6 aroma enhancement stage to supplement mid-boiling-point aroma components; and the third part is sprayed after S6 and before S7 to maximize the preservation of low-boiling-point aroma components. This batch-applied aroma enhancement method introduces spice flavor components with different volatility characteristics at their respective appropriate process stages, helping to improve the integrity and complexity of the overall product flavor. Attached Figure Description

[0029] Figure 1 This is a flowchart illustrating the preparation process of the method of the present invention. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] As attached Figure 1 The following is a quantitative braising and dynamic air-drying method for ready-to-eat braised duck necks: Example 1

[0032] The raw material pretreatment is as follows: Select 1000g of fresh or thawed frozen duck necks, remove any remaining feathers, excess fat, and visible lymph nodes from the surface, rinse repeatedly with running water until the surface is clean, drain the surface water, and set aside.

[0033] S1 microenzymatic hydrolysis treatment is as follows: Preparation of the permeation solution: Weigh 600g of purified water, add 3.0g of food-grade calcium chloride and 1.5g of compound flavor enzyme, and stir at 20℃ until completely dissolved. The mass fraction of calcium chloride in the permeation solution is 0.5%, and the mass fraction of flavor enzyme is 0.25%. Completely immerse the pre-treated duck necks in the permeation solution and place them in a programmable temperature-controlled constant temperature bath for segmented temperature-controlled enzymatic hydrolysis: the first stage is maintained at 4℃ for 35 minutes, the second stage at 28℃ for 75 minutes, and the third stage at 42℃ for 25 minutes. After enzymatic hydrolysis, remove the duck necks and drain the surface liquid.

[0034] The compound flavor enzyme is a commercially available food-grade compound flavor protease (enzyme activity not less than 5000U / g), which has both endopeptidase and exopeptidase activities; the food-grade calcium chloride has a purity of not less than 99%.

[0035] S2 vacuum low-temperature wet brine processing is as follows: Prepare the basic seasoning liquid: Weigh 780g of purified water, add 10g of salt, 12g of white sugar, 8g of dark soy sauce, and 3g of yeast extract, and stir until completely dissolved.

[0036] Preparation of the first part of the spice extract: Weigh 10g of cloves, 6g of cinnamon and 8g of star anise, crush them and pass them through a 20-mesh sieve. Add 80mL of 60% edible ethanol aqueous solution and extract at room temperature for 48 hours. Filter and concentrate the filtrate under reduced pressure at 40℃ to 20mL to obtain the first part of the spice extract.

[0037] Place the S1-treated duck necks in a vacuum braising pot, add a wet braising liquid consisting of the above-mentioned basic seasoning liquid and the first part of the spice extract at a liquid-to-material mass ratio of approximately 0.83:1, seal the pot, turn on the vacuum pump, adjust the vacuum level to -0.07 MPa, raise the temperature to 60°C and maintain this temperature for 70 minutes. After braising, release the vacuum and remove the duck necks.

[0038] S3 pulsed vacuum-assisted permeation is as follows: Place the braised duck necks (S2 grade) in a sealed vacuum container and start the pulsed vacuum program: evacuate to a pressure of -0.085 MPa and maintain for 5 minutes; then introduce sterile air to restore to normal pressure and maintain for 3 minutes. This constitutes one pulsed cycle, which is repeated 4 times. After the pulsed vacuum treatment is complete, remove the duck necks.

[0039] The S4 edible composite coating is as follows: Preparation of the coating solution: Weigh 800g of purified water, and add 12g of chitosan, 6g of sodium alginate, 12g of glycerin, 10g of xylose, and 4g of glycine in sequence. The chitosan should be dissolved in a small amount of food-grade acetic acid before being added. Add the remaining components sequentially and stir thoroughly until completely dissolved. Degas the solution using ultrasonication for 10 minutes to obtain the coating solution. The coating solution contains 1.5% chitosan, 0.75% sodium alginate, 1.5% glycerin, 1.25% xylose, and 0.5% glycine by mass.

[0040] The duck necks treated with S3 were immersed in the above coating solution and soaked for 4 minutes under a vacuum of -0.06 MPa. After soaking, the duck necks were removed and allowed to air dry naturally in a clean environment for 12 minutes.

[0041] The degree of deacetylation of the chitosan used is not less than 90%, the viscosity of sodium alginate is 200 mPa·s-400 mPa·s, the glycerol is food grade, and the xylose and glycine are both food grade.

[0042] S5 micro-fermentation coupled with dynamic air drying is as follows: Place the duck necks coated with S4 in a single layer on a stainless steel drying rack.

[0043] Preparation of compound fermentation agent suspension: The freeze-dried powders of *Lactobacillus plantarum* and *Saccharomyces hansonii* were rehydrated and activated separately with sterile water for 30 minutes, then mixed. The concentration of the bacterial solution was adjusted so that the inoculum amount of *Lactobacillus plantarum* on the surface of the duck neck after atomized spraying was 3 × 10⁻⁶. 7 The inoculum size of CFU / g duck neck raw material is 1×10⁻⁶ H⁺ d'Herpes barley yeast. 7 CFU / g duck neck raw material. The compound fermentation agent suspension is evenly sprayed onto the surface of the duck neck by atomization.

[0044] After inoculation, the duck necks were transferred to an intelligent temperature and humidity drying chamber and dynamically dried according to the following temperature and humidity gradient conditions: Phase 1: Temperature 32℃, relative humidity 75%, lasting 75 minutes; Second stage: Temperature 42℃, relative humidity 65%, lasting for 100 minutes; Phase 3: Temperature 52℃, relative humidity 50%, lasting 75 minutes.

[0045] The *Lactobacillus plantarum* used was purchased from the China Industrial Microbial Culture Collection Center, strain number CICC20265; the *Hansorius barley* was purchased from the China Industrial Microbial Culture Collection Center, strain number CICC1378.

[0046] S6 Low Heat Maillard Flavor Enhancement is as follows: Preparation of the second part of the spice extract: Weigh 8g of Sichuan pepper, 5g of cardamom, and 5g of galangal, crush them and pass them through a 20-mesh sieve. Add 70mL of 60% edible ethanol aqueous solution and extract at room temperature for 48 hours. Filter and concentrate the filtrate under reduced pressure at 40℃ to 15mL to obtain the second part of the spice extract.

[0047] Before the start of the temperature-controlled process in the S6 low-heat Maillard flavoring step, the second portion of the spice extract is evenly sprayed onto the surface of the duck necks after S5 air-drying using a misting method. The duck necks are then placed in a temperature-controlled incubator and maintained at 68°C for 20 minutes.

[0048] The S7 biological preservation process is as follows: Preparation of the third spice extract: Weigh 6g of fennel seeds, crush them and pass them through a 20-mesh sieve. Collect the distillate by steam distillation. The volume of the collected distillate is 5mL.

[0049] The actual amounts of the first, second, and third spice extracts used were 20 mL, 10 mL, and 6 mL, respectively, with a mass ratio of 5:2.5:1.5.

[0050] After the S6 constant temperature maintenance is completed, the third part of the spice extract is sprayed evenly onto the surface of the duck neck in an atomized manner.

[0051] Preparation of the compound biological preservative solution: Weigh 500g of purified water, and add 1.0g of nisin, 1.25g of ε-polylysine, 0.5g of natamycin, and 0.75g of chitosan in sequence. Adjust the pH to 4.8 with food-grade acetic acid and stir until all components are completely dissolved. The concentrations of nisin, ε-polylysine, natamycin, and chitosan in the compound biological preservative solution are 2.0g / L, 2.5g / L, 1.0g / L, and 1.5g / L, respectively.

[0052] When the surface temperature of the duck necks drops to 40℃, apply the above-mentioned composite biological preservative solution evenly to the surface of the duck necks using a misting spray method, using 15g of preservative solution per 1000g of duck necks. After application, place the duck necks in a clean environment to air dry naturally for 5 minutes.

[0053] The nisin used must have a potency of not less than 1000 IU / mg, the ε-polylysine purity must be not less than 95%, and the natamycin purity must be not less than 95%.

[0054] The S8 rapid cooling design is as follows: The S7-treated duck necks were placed in a liquid nitrogen rapid cooling tunnel. The liquid nitrogen spray volume and conveyor belt speed were adjusted to reduce the center temperature of the duck necks from 68℃ to below 4℃ within 8 minutes. After rapid cooling, the duck necks were removed from the tunnel and placed in a 4℃ environment for 45 minutes. Subsequently, the duck necks were vacuum-packed with a vacuum degree of -0.095MPa and a heat-sealing time of 2.5 seconds to obtain the ready-to-eat braised duck neck product.

[0055] Example 2: Using an alternative to papain The only difference between this embodiment and Example 1 is that in the S1 microenzymatic hydrolysis step, the compound flavor enzyme is replaced with papain of the same mass fraction (0.25%). The remaining steps, formulations, and process parameters are the same as in Example 1.

[0056] The papain used is food grade, with an enzyme activity of not less than 2000 U / mg.

[0057] Example 3: An alternative to a spice extract mass ratio of 4:2:1 The only difference between this embodiment and Example 1 is that the mass ratio of the three spice extracts is adjusted to 4:2:1. Specifically, the volume of the first spice extract is 16 mL, the volume of the second spice extract is 8 mL, and the volume of the third spice extract is 4 mL. All other steps, formulations, and process parameters are the same as in Example 1.

[0058] Example 4: An alternative to a spice extract mass ratio of 6:3:2 The only difference between this embodiment and Example 1 is that the mass ratio of the three spice extracts is adjusted to 6:3:2. Specifically, the volume of the first spice extract is 24 mL, the volume of the second spice extract is 12 mL, and the volume of the third spice extract is 8 mL. All other steps, formulations, and process parameters are the same as in Example 1.

[0059] Example 5: A substitution scheme using glucose as the reducing sugar and alanine as the amino acid. The only difference between this embodiment and Example 1 is that in the S4 edible composite coating step, xylose is replaced with an equal mass fraction of glucose (1.25%), and glycine is replaced with an equal mass fraction of alanine (0.5%). All other steps, formulations, and process parameters are the same as in Example 1.

[0060] The glucose and alanine used are both food grade, with a purity of not less than 99%.

[0061] Comparative Example 1: S1 microenzymatic hydrolysis step omitted The only difference between this comparative example and Example 1 is that the S1 microenzymatic hydrolysis step is omitted, and the duck necks are directly fed into the S2 vacuum low-temperature wet brine step after pretreatment. All other steps, formulas, and process parameters are the same as in Example 1.

[0062] The product obtained in this comparative example was compared with the product obtained in Example 1 through sensory evaluation. The sensory evaluation was conducted by 10 trained evaluators, and the evaluation indicators included flavor intensity, meat tenderness, and overall acceptability. A 9-point scoring system was used, with higher scores indicating better quality. The results are shown in Table 1.

[0063] Table 1. Sensory evaluation results of Example 1 and Comparative Example 1

[0064] Comparative Example 2: Omitted step S4 edible composite coating The only difference between this comparative example and Example 1 is that the S4 edible composite coating step is omitted, and the duck necks directly enter the S5 micro-fermentation coupled dynamic air-drying step after the S3 pulsed vacuum-assisted permeation. All other steps, formulations, and process parameters are the same as in Example 1.

[0065] The weight loss rate of the products obtained in Example 1 and Comparative Example 2 after dynamic air drying in S5 (calculated based on the weight of the duck neck after treatment in S3) and the relative content of pyrazine compounds on the surface of the products after the flavoring step in S6 were determined respectively. The relative content of pyrazine compounds was determined by headspace solid-phase microextraction-gas chromatography-mass spectrometry, with the peak area of ​​characteristic pyrazine ions in Example 1 normalized to 1.00. The results are shown in Table 2.

[0066] Table 2. Air-dried weight loss rate and relative content of pyrazine compounds in Example 1 and Comparative Example 2

[0067] Comparative Example 3: S5 micro-fermentation step omitted The only difference between this comparative example and Example 1 is that the inoculation operation of the compound fermentation agent in the S5 micro-fermentation coupled dynamic air-drying step is omitted, and the duck necks are directly subjected to pure physical dynamic air-drying under the same temperature and humidity gradient conditions after coating in S4. The remaining steps, formulas, and process parameters are the same as in Example 1.

[0068] The total free amino acid content and the number of volatile ester flavor compounds in the products obtained in Example 1 and Comparative Example 3 were determined, respectively. The total free amino acid content was determined by the ninhydrin colorimetric method, and the number of ester compounds was analyzed by headspace solid-phase microextraction-gas chromatography-mass spectrometry. Ester compounds with a matching degree greater than 85% were counted by searching the spectral library. The results are shown in Table 3.

[0069] Table 3. Content of free amino acids and types and quantities of esters in Example 1 and Comparative Example 3

[0070] Comparative Example 4: Spice extract added in one go The only difference between this comparative example and Example 1 is that the spice extracts from the first, second, and third portions are combined and added to the wet brine all at once during the S2 vacuum low-temperature wet brine step; no further spice extracts are added in subsequent steps. The total amount of the three extracts is the same as in Example 1. All other steps, formulations, and process parameters are the same as in Example 1.

[0071] The relative contents of limonene and pinene in the products obtained in Example 1 and Comparative Example 4 were determined, respectively. The relative contents of limonene and pinene were determined by headspace solid-phase microextraction-gas chromatography-mass spectrometry, with the peak areas of their respective characteristic ions in Example 1 normalized to 1.00. The results are shown in Table 4.

[0072] Table 4. Relative contents of limonene and pinene in Example 1 and Comparative Example 4

[0073] Comparative Example 5: The S7 biological preservation process was omitted and high-temperature, high-pressure sterilization was used. The only difference between this comparative example and Example 1 is that the S7 biological preservation treatment step is omitted. After the duck necks undergo S6 low-heat Maillard flavoring, they directly enter S8 rapid cooling and shaping, followed by vacuum packaging. The vacuum-packed products are then subjected to conventional high-temperature and high-pressure sterilization (sterilization conditions: temperature 121°C, time 15 minutes). All other steps, formulas, and process parameters are the same as in Example 1.

[0074] After storing the products obtained in Example 1 and Comparative Example 5 at 4°C for 15 days, the total bacterial count of the products was determined (according to GB4789.2-2022 "National Food Safety Standard - Microbiological Examination of Food - Determination of Total Bacterial Count"). Sensory evaluation was also conducted on the products, with the evaluation index being the intensity of the cooked flavor (out of 5 points, with higher scores indicating a more pronounced cooked flavor). The results are shown in Table 5.

[0075] Table 5. Total bacterial count and cooking flavor score of Example 1 and Comparative Example 5 after 15 days of storage.

[0076] The following is a supplementary explanation regarding the range of process parameters: The specific formula ratios, process temperatures, times, vacuum levels, and other parameters listed in the above embodiments are exemplary preferred embodiments and are not intended to limit the scope of protection of this invention. In actual production applications, each process parameter can be adjusted within the following ranges: In the S1 microenzymatic hydrolysis treatment, the mass fraction of calcium chloride is 0.2%-0.6%, the mass fraction of flavor enzyme is 0.1%-0.3%, and the three temperature ranges are 4℃-10℃, 25℃-30℃, and 40℃-45℃, respectively.

[0077] In the S2 vacuum low-temperature wet brine process, the vacuum degree is -0.06MPa to -0.09MPa, the liquid-to-material mass ratio is 0.8:1 to 1.2:1, and the brine temperature is 55℃-65℃.

[0078] The vacuum pressure in the S3 pulsed vacuum-assisted permeation process is -0.08MPa to -0.09MPa, the cycle time is 5 minutes to 8 minutes, and the number of cycles is 3 to 6.

[0079] The S4 edible composite coating contains 1.0%-2.0% chitosan, 0.5%-1.0% sodium alginate, 1.0%-2.0% glycerol, 1.0%-2.0% reducing sugar, and 0.3%-0.8% amino acids. The reducing sugar is xylose or glucose, and the amino acid is glycine or alanine.

[0080] In the S5 micro-fermentation coupled with dynamic air drying process, the first stage temperature was 30℃-35℃ and the relative humidity was 70%-80%; the second stage temperature was 40℃-45℃ and the relative humidity was 60%-70%; and the third stage temperature was 50℃-55℃ and the relative humidity was 45%-55%. The inoculum size of *Lactobacillus plantarum* was 1×10⁻⁶. 7 CFU / g up to 5×10 7 CFU / g duck neck raw material, Hansenula de Barry yeast inoculation amount is 5×10 6 CFU / g up to 2×10 7CFU / g duck neck raw material.

[0081] The constant temperature for the S6 low-heat Maillard flavor enhancer is 65℃-75℃, and the holding time is 15 to 30 minutes.

[0082] In the S7 biological preservation treatment, the concentrations of nisin were 1.5 g / L-2.5 g / L, ε-polylysine were 2.0 g / L-3.0 g / L, natamycin were 0.8 g / L-1.5 g / L, chitosan was 1.0 g / L-2.0 g / L, and the pH of the preservation solution was 4.5-5.0.

[0083] During the S8 rapid cooling and shaping process, the center temperature of the duck neck drops below 4°C within 10 minutes. After rapid cooling, it is left to stand in a 4°C environment for 30 to 60 minutes.

[0084] Any equivalent substitutions or simple adjustments made based on the technical concept of this invention shall be included within the scope of protection of this invention.

[0085] In conclusion, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for quantitative braising and dynamic air-drying of ready-to-eat braised duck necks, characterized in that, Includes the following steps: S1 microenzymatic hydrolysis: The pretreated duck necks are placed in a permeation solution containing calcium chloride and flavor enzymes for segmented temperature-controlled enzymatic hydrolysis. S2 Vacuum Low-Temperature Wet Braising: The duck necks treated in S1 are placed under vacuum conditions and a wet braising liquid consisting of basic seasonings, the first part of spice extract and water is added in a quantitative liquid-to-material ratio for braising. S3 Pulsating Vacuum-Assisted Permeation: The duck necks braised in S2 are alternately circulated between vacuum and normal pressure in a sealed container; S4 Edible Composite Coating: Duck necks treated with S3 are immersed in a coating solution, which is composed of chitosan, sodium alginate, glycerin, reducing sugar, amino acids and water; S5 Micro-fermentation Coupled with Dynamic Air Drying: The surface of the duck neck after S4 coating is inoculated with a compound fermentation agent, which is composed of Lactobacillus plantarum and Saccharomyces hanssonii. After inoculation, dynamic air drying is carried out under gradient temperature and humidity conditions. S6 Low-Heat Maillard Flavor Enhancement: The S5 air-dried duck necks are kept at a constant temperature below the braising temperature. S7 Biological Preservation Treatment: The surface of the duck neck after S6 flavor enhancement is coated with a composite biological preservation liquid, which is composed of nisin, ε-polylysine, natamycin, chitosan and water; S8 Rapid Cooling and Shaping: The duck necks treated with S7 are rapidly cooled with liquid nitrogen and then vacuum-packed.

2. The quantitative braising and dynamic air-drying method for ready-to-eat braised duck necks according to claim 1, characterized in that: The permeate in S1 contains 0.2%-0.6% calcium chloride by mass and 0.1%-0.3% flavor enzyme by mass. The segmented temperature-controlled enzymatic hydrolysis is carried out in three temperature ranges: 4℃-10℃, 25℃-30℃, and 40℃-45℃.

3. The quantitative braising and dynamic air-drying method for ready-to-eat braised duck necks according to claim 1, characterized in that: The vacuum condition described in S2 has a vacuum degree of -0.06MPa to -0.09MPa, a quantitative liquid-to-material ratio of 0.8:1 to 1.2:1, and a brining temperature of 55℃ to 65℃.

4. The quantitative braising and dynamic air-drying method for ready-to-eat braised duck necks according to claim 1, characterized in that: In S3, the vacuum pressure of the alternating cycle is -0.08MPa to -0.09MPa, the cycle period is 5min-8min, and the number of cycles is 3-6.

5. The quantitative braising and dynamic air-drying method for ready-to-eat braised duck necks according to claim 1, characterized in that: The coating solution described in S4 contains 1.0%-2.0% chitosan, 0.5%-1.0% sodium alginate, 1.0%-2.0% glycerol, 1.0%-2.0% reducing sugar, and 0.3%-0.8% amino acids.

6. The quantitative braising and dynamic air-drying method for ready-to-eat braised duck necks according to claim 1, characterized in that: The gradient temperature and humidity conditions described in S5 are as follows: the first stage temperature is 30℃-35℃ and the relative humidity is 70%-80%; the second stage temperature is 40℃-45℃ and the relative humidity is 60%-70%; and the third stage temperature is 50℃-55℃ and the relative humidity is 45%-55%. The inoculum size of *Lactobacillus plantarum* is 1×10⁻⁶. 7 CFU / g up to 5×10 7 The inoculum size of CFU / g duck neck raw material is 5×10⁻⁶ Hnsenula polymorpha. 6 CFU / g up to 2×10 7 CFU / g duck neck raw material.

7. The quantitative braising and dynamic air-drying method for ready-to-eat braised duck necks according to claim 1, characterized in that: The conditions below the brining temperature described in S6 are 65℃-75℃, and the constant temperature holding time is 15min-30min.

8. The method for quantitative braising and dynamic air-drying of ready-to-eat braised duck necks according to claim 1, characterized in that: The compound biological preservative solution described in S7 contains 1.5 g / L-2.5 g / L of nisin, 2.0 g / L-3.0 g / L of ε-polylysine, 0.8 g / L-1.5 g / L of natamycin, and 1.0 g / L-2.0 g / L of chitosan. The pH value of the compound biological preservative solution is 4.5-5.

0.

9. The quantitative braising and dynamic air-drying method for ready-to-eat braised duck necks according to claim 1, characterized in that: The liquid nitrogen rapid cooling described in S8 reduces the center temperature of the duck neck to below 4°C within 10 minutes. After rapid cooling, the duck neck is left to stand in a 4°C environment for 30-60 minutes before vacuum packaging.

10. The method for quantitative braising and dynamic air-drying of ready-to-eat braised duck necks according to any one of claims 1 to 9, characterized in that: The first part of the spice extract is one or more of clove extract, cinnamon extract, and star anise extract; before the constant temperature maintenance in S6, the second part of the spice extract is atomized and sprayed onto the surface of the duck neck, the second part of the spice extract is one or more of Sichuan pepper extract, cardamom extract, and galangal extract; after the constant temperature maintenance in S6 and before the biological preservation treatment in S7, the third part of the spice extract is atomized and sprayed onto the surface of the duck neck, the third part of the spice extract is fennel extract or Sichuan pepper low-boiling-point component extract; the mass ratio of the first part of the spice extract, the second part of the spice extract and the third part of the spice extract is (4-6):(2-3):(1-2).

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